1. Field of the Invention
The present invention generally relates to a method of exchanging secured data through a network, and more particularly, to a simple method of exchanging data between terminals, the data being stored in a server corresponding to each terminal, through the network.
The present invention further relates to a communication terminal and a data server that are used in the above method, and a computer program that causes a computer to perform the above method.
2. Description of the Related Art
Recent developments in mobile communication technique enabled even mobile communication terminals to exchange relatively large amounts of data through a network. Since a mobile communication terminal is desired to be light and compact, it has only a limited memory resource. The data are usually stored in a memory area of a server corresponding to each mobile communication terminal. A user can control the data through the network. Each mobile communication terminal does not need a large memory capacity, and consequently, it becomes light and consumes only low power. Mobile communication terminals include, for example, cellular phones, personal data assistants (PDA), notebook computers and so forth.
The data that the user can store in a server and control through the network include personal information of a personal information manager (PIM) software, for example, and the personal information contains directory information and calendar information, for example. The user can exchange the data of PIM software using a data format such as vCard and vCalendar promoted by the Internet mail consortium (IMC).
FIG. 1 is a schematic diagram showing an exchange of data between two communication terminals through a network. Two communication terminals 10 and 20 are connected to the Internet 100 through base stations 30 and 40, respectively. The communication terminals 10 and 20 access the server 50 through the Internet 100 and manage respective PIM information 70 and 80 using the server 50. Every user is required, when accessing the server 50 from a communication terminal 10 or 20, to go through an authentication procedure in order to protect the PIM information 70 and 80 from unauthorized access. Each user can authenticate himself or herself by sending his/her user ID to the server 50.
In the case where different users exchange their PIM information stored in different servers, one user, once being authenticated, gains access to the PIM information of the other. If the one user can freely access the PIM information of the other user, however, it is difficult to secure the PIM information of the other user.